The present invention is directed generally to industrial doors, and more particularly to a system for indicating when an industrial door has been impacted.
Industrial doors are used in a wide variety of environments for blocking and unblocking doorways through which personnel and equipment may pass. Among the common types of industrial doors are sectional doors formed of a series of panels which are hinged together to form the door. Another form of industrial door is a roller door. Typically, roller doors comprise a fabric curtain that is wound onto and off of a roller typically disposed above the doorway opening to block and unblock the doorway. Another type of industrial door is a concertina door. A concertina door is also formed of a fabric and includes straps typically attached to the leading edge of the curtain. These straps are rolled onto and off of a roller disposed above the doorway opening for the purpose of moving the curtain between blocking and unblocking positions, with the curtain folding upon itself as it is raised. While such doors are typically vertically operated, they may also be mounted for horizontal operation.
All of these illustrative industrial doors, along with other examples of such doors, may be impacted during their travel. One such impact on a door occurs when the door encounters an obstacle. For example, as an industrial door moves from an open to a closed position, an obstacle in the doorway opening may be struck by the door as it lowers. In the case of sectional doors, comprised as they typically are of rigid panels, such encountering of an obstacle may either damage the door, the obstacle, or both. Similarly, most roller and concertina doors also include a rigid bar extending across the leading edge of the curtain, which is usually the bottom edge. Typically, the rigid bottom bar serves as an anchor for straps disposed at either end of the bar which assist in pulling the door toward the closed position. Bottom bars may also serve the function of preventing the curtain in the area of the bottom bar from billowing under wind or deferential pressure conditions. Contact between the relatively rigid bottom bar and an obstacle during travel of the door can also lead to damage. One means of eliminating or minimizing such damage is for a roller door to employ a soft bottom edge such as that disclosed in co-pending U.S. patent application Ser. No. 08/437,853 assigned to the assignee of the present invention. The soft bottom bar according to that patent application minimizes any damage by deflecting and conforming to the obstacle.
Regardless of the type of door or leading edge that may be involved in an impact between an industrial door and an obstacle, the resulting damage or injury will typically be minimized if the door either stops its travel or reverses its direction of travel at the time of impact. This is particularly true when the impact is caused by a lowering door encountering an obstacle. Because of this, most such industrial doors include some type of so-called xe2x80x9creversing edge.xe2x80x9d The reversing edge is typically employed at the leading edge of the door and includes some type of sensing mechanism or electronics for determining when an obstacle has been encountered. This, in turn, causes a mechanical action or a signal to be generated which, in turn, leads a motor or other driving mechanism to stop or reverse the travel of the door. Since many of these devices are electronic, such doors may require wires to be run to or along the leading edge of the door. Moreover, such devices are subject to wear as they typically directly receive the impact being detected.
Industrial doors may also be subjected to impacts besides those occurring when the door encounters an obstacle. Impacts can also come from external sources, such as material handling equipment, running into the door. Given the high speed with which forktrucks typically travel (around 4 mph), such impacts are not uncommon. Since the vehicle or other object striking the door will be in or near the doorway when the impact occurs, it is also desirable for the door to stop or reverse its direction of travel for this type of impact as well.
The present invention is directed to an impact detection system that indicates when an industrial door has been subjected to an impact. While the preferred embodiment of the invention detects impacts at the leading edge of a vertically operated door, the detection system according to the invention may be adapted to detect an encounter between the door and an obstacle at other positions on the door besides the leading edge. Given that the detection system according to the invention plays an important safety function, an important object of the invention is providing a detection system that gives reliable and repeatable performance. In addition, it is an object of the invention to provide such an impact detection system that is simple to implement and simple in its operational details. Another object is to provide an impact detection system that is protected from the potentially harsh and active environment of an industrial door.
In accordance with these and other objects of the present invention, a novel impact detection system is provided. In its broadest sense, the impact detection system comprises two members that are releasably coupled to each other and that, when they are coupled, move together with the door as it travels. A first member preferably extends beyond the doorway opening, and is protected from the doorway environment. Also disposed beyond the doorway opening is a radiation emitter and a radiation detector, preferably packaged together in a photoeye device. The photoeye emits a beam of radiation, typically in the direction of travel of the door. The first member carries a reflector that, when the two members are coupled, reflects the radiation back to the photoeye. According to the invention, however, this reflector is also movable to a position wherein it does not reflect the radiation back to the photoeye in response to separation of the two members caused by the door being impacted. A releasable coupling between the first member and second member is designed to provide such separation when the door encounters an impact above a certain magnitude. The change in state from 1) the radiation being reflected to the photoeye to 2) the radiation not being reflected to the photoeye thus serves as an indication that an impact on the door has been detected.
According to the preferred embodiment of the invention, the obstacle detection system is adapted for use with a fabric roller door. The roller door includes enclosures on either side of the door which receive the lateral edges of the curtain. The photoeye is housed within such an enclosure, thus protecting the photoeye and its radiation beam from the environment of the door. Further, the first of the two releasably coupled members, and the reflector that is carried with the first of the members, are also received within this enclosure. The second of the two members, according to one embodiment, is a cable which extends across the width of the door in a preferably stretched condition. In an alternative embodiment, the second member is a plate fixed to a lateral edge of the door. Impact on the door, such as by contact between the door and an obstacle, causes release of the releasable coupling between the first member and the second member. This in turn causes the reflector to move between its two positions. The first of the two members also preferably includes a bias member that biases the reflector toward its non-reflecting position in response to separation of the releasable coupling between the two members.